光果甘草叶中性多糖结构表征及抗氧化活性研究

Structural Characteristics and Antioxidant Activity of Polysaccharides from Glycyrrhiza glabra L. Leaf

本文以光果甘草叶为原料,提取得到水溶性多糖GC C,采用DEAE-Sepharose Fast Flow柱层析法对GC C进行分离纯化,得到一种中性多糖（GC I）,两种酸性多糖（GC II和GC III）,选择DPPH自由基清除能力、氧自由基吸收能力（ORAC）强的中性多糖GC I,对其进行结构特征分析。采用高效凝胶渗透色谱法（GPC）、红外光谱法（FT-IR）、PMP柱前衍生-高效液相色谱法（HPLC）、甲基化-气相色谱质谱法（GC-MS）测定GC I的分子量、单糖组成以及糖苷键连接方式。GC I含有两个分子量分布不同的多糖,它们的平均分子量分别为980 ku及20 ku;红外光谱中4000~500 cm-1波数范围内出现了多糖的特征峰;GC I由5种单糖组成,包括：甘露糖、鼠李糖、葡萄糖、半乳糖和阿拉伯糖;GC I中→2）-Araf-（1→、→6）-Galp-（1→和→6）-Glcp-（1→残基含量最高。

A crude water-soluble polysaccharide（GC C） was obtained from Glycyrrhiza glabra L. Leaf by water extraction. DEAE-Sepharose fast flow column chromatography was used to separate and purify GC C to obtain one neutral polysaccharide（GC I） and two acidic polysaccharides（GC II and GC III）. The strongest 2, 2-diphenyl-1-picrylhydrazyl（DPPH） radical scavenging activity and oxygen radical absorbance capacity（ORAC） were detected in GC I, which was therefore selected for structural characterization. The molecular weight, monosaccharide composition, and glycosidic linkages of GC I were determined by high performance gel permeation chromatography（GPC）, infrared spectroscopy（FT-IR）, 1-phenyl-3-methyl-5-pyrazolone（PMP） precolumn derivatization-high performance liquid chromatography（HPLC）, and methylation-gas chromatography mass spectrometry（GC-MS）. It was found that GC I consisted of two polysaccharides with average molecular weights of 980 k Da and 20 k Da. The FT-IR spectra showed the characteristic peaks of the polysaccharides were in the frequency range of 4000-500 cm-1. Monosaccharide composition analysis indicated that GC I contained mannose, rhamnose, glucose, galactose, and arabinose, The residues of →2）-Araf-（1→, →6）-Galp-（1→ and →6）-Glcp-（1→ showed thehighest amounts in GC I.